1. Field of the Invention
The present invention relates to a hold type image display unit as typified by a liquid crystal display unit, and more particularly, it relates to an image display unit which can reduce blurriness of a moving image.
2. Description of the Related Art
As image display units, there are an impulse type display unit which strongly emits light in a moment that an image is written like a display unit using a cathode ray tube (CRT), and a hold type display unit which holds display from writing of an image to writing of an image of a next frame like an active matrix type display unit having a memory function per each pixel. As the active matrix type display unit, there is a liquid crystal display unit using a thin-film transistor (TFT). In the liquid crystal display unit, an image written in a pixel by a TFT and a capacitor arranged for each pixel is held for a fixed time.
Since a response speed of the liquid crystal display unit is slow, the liquid crystal display unit has a problem that an after-image is generated when a moving image is displayed. As a one of methods which can suppress this problem, there is a method using a filter which emphasizes a video signal in a direction of the time base (time base emphasizing circuit).
The hold type display unit such as a liquid crystal display unit, however, cannot solve blurriness (which will be referred to as a moving image blur) of a moving image caused due to an influence of a visual system integration owing to hold display itself even if a response speed of the liquid crystal is increased.
This problem and its solution are described in “Fundamental Deterioration of Picture Quality for Moving Images Displayed on LCDs and Methods for Improvement” by Taiichiro Kurita, Technical Report of IEICE EID2000-47 (2000-09), p. 13-18. It is to be noted that a moving image blur is not restricted to the liquid crystal display unit, and it is likewise generated in an active matrix type display unit even if this display unit is an organic electroluminescence display unit. As solutions of the moving image blur, the above-mentioned reference describes a first method which shortens a hold time and approximates it to that in display of an impulse type display unit, and a second method which increases a frame frequency of an input video signal having a frame frequency of 60 Hz to a twofold value which is 120 Hz by motion compensating means.
The first method has a drawback (first problem) that means for shutting a backlight in synchronization with a video signal is required and display without flicker which is an advantage of the hold type display is deteriorated. The second method has an disadvantage (second problem) that a sampling frequency of a video signal and a writing speed of the liquid crystal must be respectively doubled in order to double a frame frequency, which imposes a great burden on an operating speed of a circuit or a connection interface between circuits, thereby involving an actual difficulty.